| Nowadays, the development of urban railway system in our country is at a bursting age. Many large cities have been built or are ready to start to build the subway. The challenge of complex geological conditions which sandy gravel layer belongs to is inevitable with lots of tunneling projects going on across the country. The particles of sandy gravel layer with large porosity and no cohesion with each other are easy to collapse when the shield cutter cut the soil, which is enormous difficulties and challenges engineer faced during the shield excavating. There are lots of research about tunnel face stability during tunnel construction while the flow characteristics of the sand particles is little and lack in view of the real simulation for TBM tunneling process too. Based on Lanzhou metro line 1, the law of particle flow and surface subsidence control were studied about earth pressure balance shield construction with the discrete element numerical simulation method used. The major works of this dissertation are as follows:(1) Firstly, a large scale triaxial test (30cm) was done to obtain the stress-strain curve of the sandy pebble stratum of Lanzhou in lab. Then the micro parameters of the sandy pebble stratum in Lanzhou were obtained basing on the comparison of the numerical experiments and laboratory test.(2) Three-dimensional mechanical model of panel and spoke shield machine were build by Soildworks software and imported into the discrete element model. Research on interaction between particles and shield and the pressure of soil chamber had been done by setting the motion state of the mechanical model.(3) In order to obtain the law of the surface deformation and movement of the particles in different depth during the different shield tunneling, a three-dimensional discrete element model was established. And the data got from the numerical model were compared with field monitoring data to verify the correctness of the discrete element model. |
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